Summary and Relevance of Proposed Research Humans and other advanced animals have a remarkable capacity to rapidly acquire knowledge about our environment and to learn a wide array of complex tasks. Recent work has shown the importance of mental ?schema? in generalizing knowledge learned from simpler tasks and concepts, allowing rapid learning of new tasks and knowledge built upon the cognitive scaffold provided by earlier learning sets. For example, learning a simple card game like ?war? or ?old maid? facilitates learning of more complex games such as ?spades? or ?bridge?, which build on knowledge or schema from simpler games. Although neurophysiological studies of hippocampal-cortical interactions during complex behavior and learning have been conducted extensively in rodents, there is a surprising lack of knowledge about the patterns of hippocampal neuronal activity or cortical- hippocampal interactions which underlie rapid learning and the development of mental schema in humans and other advanced animals. This project will take advantage of a newly available large-scale semi-chronic neurophysiological approach to understand the interactions between hippocampus, parietal cortex, and prefrontal cortex, which underlie both the development of schema and use of schema for rapid visual associative and abstract category learning. While much is known about how the brain processes simple sensory features (such as color, orientation, and direction of motion), less is known about how the brain learns and represents the meaning, or category, of stimuli, and how categorical knowledge is generalized to learn new tasks and concepts. A greater understanding of learning and categorization is critical for addressing a number of brain diseases, conditions, and mental illnesses (e.g. stroke, Alzheimer?s disease, attention deficit disorder, schizophrenia, and stroke) that leave patients impaired in everyday tasks that require visual learning, recognition and/or evaluating and responding appropriately to sensory information. The long-term goal of this project is to guide the next generation of treatments for these brain-based diseases and disorders by helping to develop a detailed understanding of the brain mechanisms that underlie learning, memory and decision making. These studies also have relevance for understanding and addressing learning disabilities, such as attention deficit disorder and dyslexia, which affect a substantial fraction of school age children and young adults. Thus, a more detailed understanding of the basic brain mechanisms underlying learning and attention will likely give important insights into the causes and potential treatments for disorders involving these cognitive faculties.